The present invention relates to apparatus for cutting tubes. It is particularly adapted to cutting paper tubes. Paper tubes have a number of uses in various industries. They are of particular utility in the electrical and electronics industries where they are used for forms for coils, transformers, inductors and the like. The size of the paper tube varies with the application, but paper tubes have been made ranging in size from less than a quarter of an inch O.D. to as great as seven inches O.D. Further, depending upon the application, the thickness of the wall of the tube may vary from a very thin tube to one having a wall thickness of 175 mils. Different techniques have been used for cutting paper tubes in the industry. For example, for small, thin-walled tubes which are flexible and somewhat difficult to saw, a snap cutter of the type disclosed in my copending application for "Snap-Cutter for Paper Tubes", Ser. No. 806,106, filed June 13, 1977, are successful. Where the tubes are made on an automatic winding machine, such a machine may be equipped with conventional saws for cutting the tubes into the longer lengths normally found in the initial manufacturing stages. That is, a plurality of tapes are wound onto an arbor in a continuous fashion and laminated together adhesively. In this initial stage, the tubes are cut to relatively long lengths, and taken to a separate location for cutting into the shorter, more precise lengths required by the customer.
Another technique used in cutting smaller thin-walled tubes is to hold the tubes in such a fashion that they can be surface-driven at a relatively high speed and then moved into cutting position. Although this technique may be used for smaller tubes, it, as well as other known techniques, have proven difficult in the cutting of larger tubes (because of the design involved, up to seven inches O.D., for example) as well as in the cutting of thick tubes (having a wall thickness of approximately 170 mils. and an O.D. of approximately 31/2 inches).
According to the present invention, apparatus includes a cradle for holding a tube to be cut. The cradle is mounted for rotation about its axis. A plurality of saws are mounted on a shaft having its axis parallel to the axis of the cradle, and the saws are driven at high speed during operation. The cradle is rotated between a loading position in which the tubes are placed in the cradle, and a cutting position adjacent the saws. Surface drive means are provided adjacent the cutting station for spinning the tube held in the cradle. Thus, the cradle can be rotated at a fairly high speed from the loading position through the cutting position and back to the loading position. In other words, one complete revolution of the cradle defines a cutting cycle.
In the case of thick-walled paper tubes (for example, tubes having a thickness in the range of 0.100-0.200 inches), the cradle is brought to a stop for a limited period of time of the order of two seconds just as the tube enters the cutting station to enable saws to make partial peripheral cuts in the tube. This momentary interruption in the rotation of the cradle enables the saws to cut thick-walled tubes without causing a bend in the tube, and while permitting the cradle to rotate through its cycle at a high speed, except for the momentary stop at the initiation of cutting. The high-speed rotation of the cradle is important when it is considered that paper tubes of this type are cut at the rate of 150-200 tubes per hour. Such savings in time in the operating cycle of the machine greatly increase production.
The present invention thus provides for tube-cutting apparatus which is adaptable for a wide range of outer diameters and wall thicknesses of paper tubes. Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.